Functional diversity and identity of plant genotypes regulate rhizodeposition and soil microbial activity.

Our understanding of the linkages between plant diversity and soil carbon and nutrient cycling is primarily derived from studies at the species level, while the importance and mechanisms of diversity effects at the genotype level are poorly understood. Here we examine how genotypic diversity and identity, and associated variation in functional traits, within a common grass species, Anthoxanthum odoratum, modified rhizodeposition, soil microbial activity and litter decomposition. Root litter quality was not significantly affected by plant genotypic diversity, but decomposition was enhanced in soils with the legacy of higher genotypic diversity. Plant genotypic diversity and identity modified rhizodeposition and associated microbial activity via two independent pathways. Plant genotypic diversity enhanced soil functioning via positive effects on variation in specific leaf area and total rhizodeposition. Genotype identity affected both rhizodeposit quantity and quality, and these effects were mediated by differences in mean specific leaf area, shoot mass and plant height. Rhizodeposition was more strongly predicted by aboveground than belowground traits, suggesting strong linkages between photosynthesis and root exudation. Our study demonstrates that functional diversity and identity of plant genotypes modulates belowground carbon supply and quality, representing an important but overlooked pathway by which biodiversity affects ecosystem functioning.

Keystone microbial taxa drive the accelerated decompositions of cellulose and lignin by long-term resource enrichments.

Lignin and cellulose are the most important component of crop straw entering arable soil. The decomposition of lignin and cellulose are related to carbon sequestration and soil fertility. The keystone microbes decomposing lignin and cellulose in cropland and their impact on agricultural management, however, remains largely unclear. In this study, we traced the carbon (C) from highly enriched 13C-labeled (atom% 13C = 99 %) lignin and cellulose to functional keystone microbes in soils of a 26-year fertilization field experiment with stable isotope probing (SIP). 13C-cellulose and 13C-lignin decomposition were significantly accelerated with the long-term application of fertilization, especially with the combination of organic and chemical fertilization (NPKM). The 13C was mainly assimilated by bacteria Acidobacteria (i.e. GP1, GP3, GP6), Proteobacteria (i.e. unidentified gamaproteobactiera, Bradyrhizobium), and fungi Ascomycota (i.e. Talaromyces and Fusarium, etc.). The keystone bacteria taxa decomposing cellulose and lignin were large overlapped, but substantially shaped by fertilization. For instance, GP3 was the dominant bacterium that decomposed both cellulose and lignin in no fertilizer control (CK), while GP1 and GP6 were the ones in chemical fertilization (NPK) and NPKM, respectively. The decomposition rates of cellulose in different fertilizations were majorly predicted by soil total phosphorus (TP), functional fungi abundance, total nitrogen (TN), whereas functional bacterial and fungal abundance, TP, and community structure of functional fungi manipulated the decomposing rate of lignin. Together, we demonstrate that keystone functional microbes decomposing cellulose and lignin were largely concurring and significantly altered by long-term resources enrichment, which drives the similar patterns of decomposition rates of these two substrates along the resource enrichment gradient.

Characterization of a novel ß-thioglucosidase CpTGG1 in Carica papaya and its substrate-dependent and ascorbic acid-independent O-ß-glucosidase activity.

Plant thioglucosidases are the only known S-glycosidases in the large superfamily of glycosidases. These enzymes evolved more recently and are distributed mainly in Brassicales. Thioglucosidase research has focused mainly on the cruciferous crops due to their economic importance and cancer preventive benefits. In this study, we cloned a novel myrosinase gene, CpTGG1, from Carica papaya Linnaeus. and showed that it was expressed in the aboveground tissues in planta. The recombinant CpTGG1 expressed in Pichia pastoris catalyzed the hydrolysis of both sinigrin and glucotropaeolin (the only thioglucoside present in papaya), showing that CpTGG1 was indeed a functional myrosinase gene. Sequence alignment analysis indicated that CpTGG1 contained all the motifs conserved in functional myrosinases from crucifers, except for two aglycon-binding motifs, suggesting substrate priority variation of the non-cruciferous myrosinases. Using sinigrin as substrate, the apparent K(m) and V(max) values of recombinant CpTGG1 were 2.82 mM and 59.9 µmol min⁻¹ mg protein⁻¹ , respectively. The K(cat) /K(m) value was 23 s⁻¹ mM⁻¹ . O-ß-glucosidase activity towards a variety of substrates were tested, CpTGG1 displayed substrate-dependent and ascorbic acid-independent O-ß-glucosidase activity towards 2-nitrophenyl-ß-D-glucopyranoside and 4-nitrophenyl-ß-D-glucopyranoside, but was inactive towards glucovanillin and n-octyl-ß-D-glucopyranoside. Phylogenetic analysis indicated CpTGG1 belongs to the MYR II subfamily of myrosinases.

Network meta-analysis of percutaneous vertebroplasty, percutaneous kyphoplasty, nerve block, and conservative treatment for nonsurgery options of acute/subacute and chronic osteoporotic vertebral compression fractures (OVCFs) in short-term and long-term effects.

BACKGROUND: Osteoporotic vertebral compression fractures (OVCFs) commonly afflicts most aged people resulting back pain, substantial vertebral deformity, functional disability, decreased quality of life, and increased adjacent spinal fractures and mortality. Percutaneous vertebral augmentation (PVA) included percutaneous vertebroplasty (PVP) and percutaneous kyphoplasty (PKP), nerve block (NB), and conservative treatment (CT) are used for the nonsurgery treatment strategy of OVCFs, however, current evaluation of their efficacy remains controversial. METHODS AND ANALYSIS: A systematic literature search was carried out in PubMed, EMBASE, Web of Knowledge, and the Cochrane Central Register of Controlled Trials up to October 31, 2017. Randomized controlled trials (RCTs) were compared PVP, PKP, NB, or CT for treating OVCFs. The risk of bias for each trial was rated according to the Cochrane Handbook. Mean differences (MDs) with 95% confidence intervals (CIs) were utilized to express VAS (visual analog scale) outcomes. The network meta-analysis (NMA) of the comparative efficacy measured by change of VAS on acute/subacute and chronic OVCFs was conducted for a short-term (<4 weeks) and long-term (≥6-12months) follow-up with the ADDIS software. RESULTS: A total of 18 trials among 1994 patients were included in the NMA. The PVA (PVP and PKP) had better efficacy than CT. PKP was first option in alleviating pain in the case of the acute/subacute OVCFs for long term, and chronic OVCFs for short term and long term, while PVP had the most superiority in the case of the acute/subacute OVCFs for short term. NB ranks higher probability than PKP and PVP on acute/subacute OVCFs in short and long-term, respectively. CONCLUSIONS: The present results suggest that PVA (PVP/PKP) had better performance than CT in alleviating acute/subacute and chronic OVCFs pain for short and long-term. NB may be used as an alternative or before PVA, as far as pain relief is concerned. Various nonsurgery treatments including CT, PVA (PVP/PKP), NB, or a combination of these treatments are performed with the goal of reducing pain, stabilizing the vertebrae, and restoring mobility.